ADTypes.jl is a multi-valued logic system to choose an automatic differentiation (AD) package and specify its parameters.
See the API reference in the documentation. If a given package is missing, feel free to open an issue or pull request.
A natural approach is to use a keyword argument with e.g. Bool or Symbol values.
Let's see a few examples to understand why this is not enough:
autodiff = true: ambiguous, we don't know which AD package should be usedautodiff = :forward: ambiguous, there are several AD packages implementing both forward and reverse mode (and there are other modes beyond that)autodiff = :Enzyme: ambiguous, some AD packages can work both in forward and reverse modeautodiff = (:Enzyme, :forward): not too bad, but many AD packages require additional configuration (number of chunks, tape compilation, etc.)
A more involved struct is thus required, with package-specific parameters. If every AD user develops their own version of said struct, it will ruin interoperability. This is why ADTypes.jl provides a single set of shared types for this task, as an extremely lightweight dependency. They are types and not enums because we need AD choice information statically to use it for dispatch.